1. Field of the Invention
The present invention relates to novel stable aqueous suspensions of precipitated silica particulates and to the use of such novel suspensions, particularly in the papermaking industry.
2. Description of the Prior Art
Aqueous slurries or suspensions of silicas are known to this art to be useful for a number of different applications, in particular in the papermaking industry, for the coating of various paper substrates.
Nonetheless, these suspensions have a tendency to suffer from gelling or sedimentation, which makes them difficult to transport or store. Indeed, it very frequently occurs that the formation of a gel or the deposit of a hard layer of pigment, above which a slurry forms which is more fluid but which has a low content of dry solids, is observed at the end of a transportation operation or after storage over a period of time of greater or lesser duration. In addition, it is often impossible to resuspend the silica or to produce a slurry which has a sufficiently low viscosity that it can be pumped and therefore used on an industrial scale. Thus, a pronounced problem exists in this art, which becomes all the more acute when attempts are made to produce suspensions having a high content of dry solids.
French Patent Application No. 2,414,387 and European Patent Application No. 194,116 describe processes for the stabilization of silica slurries using xanthan gum or a quaternary ammonium compound. However, such applications essentially relate to slurries of silica gel, the precipitated silica-base suspensions which are stabilized by the described processes not exceeding a level of concentration on the order of 10%.